1. Field of the Invention
The invention relates generally to sealing structures for applications to the periphery of a door or like opening and more specifically to heavy duty sealing structures for loading dock shelters that form an environmental seal between the warehouse interior and the exterior environment.
2. Background of the Invention
Loading docks contain doors that allow access from the exterior to the interior of a warehouse or other storage facility, and are used for loading and unloading cargo from freight trucks. Trucks reverse against the loading dock, and the sides and top may contain sealing structures which attempt to seal the cargo body of the truck such that the elements do not enter the warehouse and goods can then be moved between the cargo body and the warehouse. The seals attempt to prevent snow and rain from entering, but also attempt to reduce air exchange, for instance cold outside air from entering a heated warehouse, as well as preventing uncomfortable drafts.
Sealing structures of the above-mentioned general type are known in the art. Dock shelters consist of a framework that extends up to three feet out from the loading dock wall, and curtains may hang from this frame to drape over the top and either side of the docked cargo body. However, these curtains tend to be limp and may create a poor appearance. While acceptable in milder climates, they may not seal optimally in a windy or cold environment. Other arrangements include foam pads to which the cargo bodies are backed, and which seal as a result of compression of the foam. While these provide a seal, they are not ideal because the foam is prone to wear from contact with the cargo bodies and cargo doors. Additionally, foam seals may be more expensive than traditional dock shelters, and may reduce the access area of the trailer because the foam pads overlap the perimeter of the cargo body.
A further arrangement is shown in U.S. Pat. No. 4,359,846 which has three flexible sealing elements along the top and sides of the loading dock entrance, which are movable from an inoperative position flush with the loading dock entrance, to an operative position which attempts to seal the loading dock entrance into the truck cargo body. This configuration requires effort to extend the sealing lamellas into the cargo body which is not practical and causes further delay in the loading or unloading of a cargo body. As well, the seal is maintained by the use of springs which hold the lamellas in contact with the truck body, which are subject to mechanical breakdown and increased cost of manufacture.
It is also known to subdivide the flexible walls into several individual lamellas which are arranged parallel to one another, in order to provide improved matching of the walls to the outer contour of the container, such as is described in U.S. Pat. No. 5,333,424. The lamellas in this configuration are prone to abuse by the truck cargo bodies which reverse against them as several lamellas are held in a compressed state over the entire period of use. Furthermore, the lamellas are also prone to tearing with the uneven edges of the cargo body or the cargo doors, which fold around the side of the cargo body when fully open.
U.S. Pat. No. 3,854,257 discloses a sealing structure which is composed, on each side of the loading dock, of two sheets of flexible material, the front sides being joined together face to face, secured at one side, with the opposite sides bent backwards and secured to the loading dock to create a bumper that compresses when the truck contacts it. This design has shortcomings in that it uses two pieces to form the seal, making it mechanically complex and expensive to manufacture, and the inner joint is subject to wear leading to breakdowns. Similar disadvantages as outline above are present in this application as seals are maintained in a compressed state during any use which leads to the seals deteriorating quickly.
A further arrangement is disclosed in U.S. Pat. No. 6,948,285, wherein a dock shelter is described with face panels on both sides and on top, which are moveable for sealing against vehicles of various sizes. This arrangement is more durable than foam, but due to the use of springs it is mechanically complex, therefore less robust as well as expensive to manufacture.
Based on the above, there is a need for a sealing structure that will sealingly engage with a container regardless of the openings of the container to unload and load cargo. The present invention provides a sealing structure which allows the container to be environmentally sealed to the area of loading or unloading within a building, and addresses the shortcomings identified in the prior art by being less expensive to manufacture, more durable and a having a greater service life. The sealing structure of the present invention also does not require the use of a significant and considerable compression force to be exerted by the cargo body to maintain a sealing environment.